1. Field Of The Invention
The present invention relates to a transmission device provided in a tire cavity region for transmitting tire information related to the condition of the tire, a tire assembly, and a tire condition monitoring system for determining the presence of an abnormality in a tire.
2. Description Of The Related Art
Inspections of the air pressure of tires mounted on a vehicle have conventionally been desired from the point of view of improvements in tire durability, abrasion resistance and fuel consumption, or improvement in ride comfort and maneuverability. As a result, various types of tire pressure monitoring systems have been proposed. These systems generally include a transmission device that detects air pressure information of the tires mounted on a vehicle and transmits that information, and the systems obtain the air pressure information of the tires from the transmission device and monitor the air pressure of the tires.
Conversely, a puncture repair agent to be injected inside the tire cavity region interposed between the tire and the rim is often used when a puncture occurs in a tire. Since the puncture repair agent is a liquid, the puncture repair agent adheres to the inner surface of the tire that faces the tire cavity region and even adheres to the transmission device provided in the tire cavity region when the puncture repair agent is injected into the tire cavity region. In some cases, the puncture repair agent solidifies and covers an opening provided in the transmission device thus becoming a problem that adversely affects the measurement of the air pressure.
To address this problem, a wheel condition detection device has been proposed that is capable of retaining a normal detection condition by preventing the intrusion of foreign matter from a communicating part for detection as described in Japanese Patent Laid-open No. 2008-62730.
Specifically, a communicating part open and close mechanism that opens and closes a air inlet hole provided in a case is provided on a tire pressure monitoring system (TPMS) valve of the wheel condition detection device. The puncture repair agent is restricted from intruding into a detection space through the air inlet hole when a puncture is being repaired. The communicating part open and close mechanism is configured by a mechanical mechanism that includes a cover and a helical torsion spring, and the air inlet hole is automatically opened and closed due to the centrifugal force acting on the wheel.
Moreover, a tire pressure monitoring system and a tire pressure sensor unit have been proposed that are capable of informing a driver about the possibility that the tire pressure is low after the use of a puncture repair agent when repairing a puncture as described in Japanese Patent Laid-open No. 2007-196834.
Specifically, the tire pressure monitoring system is equipped with a sensor unit provided in each tire of a vehicle and having and air pressure sensor and a transmitter, a receiver for receiving radio waves from the sensor units, and a control ECU for issuing an alarm when the pressure of a tire meets or falls below a threshold. The system includes a puncture determining means for determining the presence of a puncture in each tire and a puncture repair agent usage determining means for determining whether a puncture repair agent is used when repairing a puncture, and the control ECU continues to issue the alarm even if the tire pressure value from the pressure sensor is a normal value when it is determined that a punctured tire was repaired using the puncture repair agent.